Prehistoric qubits: experiments testing the fundamental physics of superconducting quantum devices

The physics Nobel prize of 2025 was awarded for pioneering experiments on the current-biased Josephson junction, showing macroscopic quantum tunneling and energy-level quantization. I will describe the fundamental understanding of its physics, including the need for microwave engineering of the device, filtering of noise, and measurement of the device parameters. Important checks will be explained. I will also briefly review a few experiments that led to the development of quantum computers, leading to the demonstration of powerful computing in the quantum supremacy experiment. Finally, I will explain my view of the future, the need for advanced manufacturing.